System and method for active bypass dialysis access disconnection detection

ABSTRACT

A dialysis system comprising: a blood circuit including a blood pump, a dialyzer, and an air removal apparatus; an arterial line of the blood circuit extending from the blood pump to an arterial access needle; a venous line of the blood circuit extending from the air removal apparatus to a venous access needle; arterial and venous conductive connections placed along the arterial and venous lines, respectively; a first electrical potential source configured to apply a first electrical potential between (i) the arterial and venous conductive connections and (ii) the arterial and venous access needles; and a second electrical potential source configured to apply a second electrical potential between (a) the arterial and venous conductive connections and (b) one of the blood pump, dialyzer or air removal device.

PRIORITY

This application claims priority to and the benefit as a continuationapplication of U.S. patent application Ser. No. 13/157,010, entitled“Systems And Methods For Dialysis Access Disconnection”, filed Jun. 9,2011, which is a continuation of U.S. Pat. No. 7,959,594, entitled“Access Disconnection Systems And Methods,” filed Jan. 25, 2006, whichis a continuation of U.S. Pat. No. 7,022,098, entitled “AccessDisconnection Systems And Methods”, filed Apr. 10, 2002, the entirecontents of each of which are expressly incorporated herein by referenceand relied upon.

BACKGROUND OF THE INVENTION

The present invention relates generally to patient access disconnectionsystems and methods for medical treatments. More specifically, thepresent invention relates to the detection of patient accessdisconnection, such as dislodgment of a patient access device duringmedical treatments or therapies including dialysis therapy.

A variety of different medical treatments relate to the delivery offluid to and/or from a patient, such as the delivery of blood between apatient and an extracorporeal system connected to the patient via aneedle or needles or any suitable access device inserted within thepatient. For example, hemodialysis, hemofiltration and hemodiafiltrationare all treatments that remove waste, toxins and excess water directlyfrom the patient's blood. During these treatments, the patient isconnected to an extracoporeal machine, and the patient's blood is pumpedthrough the machine. Waste, toxins and excess water are removed from thepatient's blood, and the blood is infused back into the patient. Needlesor other suitable access devices are inserted into the patient'svascular access in order to transfer the patient's blood to and from theextracoporeal machine. Traditional hemodialysis, hemofiltration andhemodiafiltration treatments can last several hours and are generallyperformed in a treatment center about three to four times per week.

During any of these hemo treatments, dislodgment of the access devicecan occur, such as dislodgment of a needle inserted into the patient'svascular access including an arterio-venous graft or fistula. If notdetected immediately, this can produce a significant amount of bloodloss to the patient. The risks associated with a needle dislodgment areconsiderable. In this regard, important criteria for monitoring bloodloss include, for example, the sensitivity, specificity and responsetime with respect to the detection of needle dislodgment. With increasedlevels of sensitivity, specificity, and response time, the detection ofneedle dislodgment can be enhanced, and blood loss due to dislodgmentcan be minimized.

Typically, patients undergoing medical treatment, such as hemodialysis,hemofiltration or hemodiafiltration, are visually monitored in order todetect needle dislodgment. However, the needle may not be in plain viewof the patient or medical staff (i.e., it may be covered by a blanket)such that it could delay detection and, thus, responsive actions to betaken in view of dislodgment, such as stopping the blood pump of theextracorporeal machine to minimize blood loss to the patient.

Moreover, in view of the increased quality of life, observed reductionsin both morbidity and mortality and lower costs than in-centertreatments, a renewed interest has arisen for self care and home hemotherapies. Such home hemo therapies (whether hemodialysis,hemofiltration or hemodiafiltration) allow for both nocturnal as well asdaily treatments. During these self care and home hemo sessions,especially during a nocturnal home hemo session, when the patient isasleep, dislodgment risks are more significant because nurses or otherattendants are not present to detect the dislodgment.

Although devices that employ a variety of different sensors areavailable and known for detecting and/or monitoring a variety ofdifferent bodily fluids, these devices may not be suitably adapted todetect needle dislodgment. For example, known devices that employsensors including pH, temperature and conductivity have been utilized todetect bedwetting and diaper wetness. Further, devices that employpressure sensors and/or flow sensing devices are known and used duringmedical treatment, such as dialysis therapy, to monitor fluid flowincluding blood flow to and/or from the patient. However, these types ofdetection devices may not provide an adequate level of sensitivity andresponsiveness if applied to detecting blood loss from the patient dueto needle dislodgment. Although venous pressure is known to be used tomonitor needle dislodgment, it is not very sensitive to needle drop-out.

Additional other devices and methods are generally known to monitorvascular access based on the electrical conductivity of blood. Forexample, Australian Patent No. 730,338 based on PCT Publication No. WO99/12588 employs an electrical circuit which includes two points throughwhich current is induced into blood flowing in an extracorporeal circuitthat forms a closed conductor loop. Current is induced in blood using acoil that is placed around the outside of the tubing of the bloodcircuit. Thus, each coil does not directly contact the blood as itcirculates through the tubing. In this regard, a current is generatedinto the blood flowing in the extracorporeal circuit by an alternatingcurrent that flows through one of the coils. The second coil is thenutilized to measure a change in amperage of the induced current as itflows through the blood circuit.

In this regard, electrical current is coupled to a blood treatmentsystem that includes a number of high impedance components, such a bloodpump, air bubble traps, pinch clamps and/or the like. Because of thelarge impedance of the conducting fluid loop (due to the peristalticpump and other components), the induction and detection of apatient-safe current requires an impractically complex design of thecoil and system. Further, a high level of noise would necessarily resultfrom the use of such levels of induced current. This can adverselyimpact the sensitivity of detection. If lower currents are used, thefield coil would have to be increased in size to detect such low currentlevels. This may not be practical in use, particularly as applied duringdialysis therapy.

PCT Publication No. WO 01/47581 discloses a method and device formonitoring access to the cardiovascular system of a patient. The accessmonitoring employs an electrical circuit which can generate and detect acurrent at separate points along a blood circuit connected to thepatient. Current is injected into blood using capacitive couplers thateach have a metal tube placed around the blood circuit tubing. In thisregard, the metal tube defines a first plate of a capacitor; the bloodcircuit tubing defines the dielectric; and the blood inside of the bloodcircuit tubing defines the second plate of the capacitor.

The generator applies a potential difference between a pair ofcapacitive couplers to generate a current in blood flowing through theblood circuit. A detector utilizes an additional and separate pair ofcapacitive couplers to measure the current along at least one section ofthe venous branch between a first contact point and the venous needle.The change in voltage (dV) can then be determined based on a measuredchange in current and compared to a reference range (I) to monitoraccess conditions. In this regard, PCT Publication No. WO 01/47581requires a complex circuit design that utilizes multiple sets ofcapacitive couplers to monitor vascular access conditions. This canincrease the cost and expense of using same.

Further, the mere use of capacitive coupling to inject an electricsignal in the blood circuit and/or for detection purposes can beproblematic. In this regard, the signal must pass through the tubing ofthe blood circuit as the tubing acts as a dielectric of the capacitor.This may cause an excess level of noise and/or other interference withrespect to the detection of changes in vascular access conditions.

In this regard, it is believed that known devices, apparatuses, systems,and/or methods that can be used to monitor a patient's access conditionsmay not be capable of detecting change in access conditions, such as inresponse to needle drop out, with sufficient sensitivity and specificityto ensure immediate detection of blood loss such that responsivemeasures can be taken to minimize blood loss. As applied, if twentyseconds or more of time elapses before blood loss due to, for example,dislodgment of the venous needle, over 100 milliliters in blood loss canoccur at a blood flow rate of 400 ml/min, which is typical of dialysistherapy. Thus, the capability to respond quickly upon immediatedetection of dislodgment of an access device, such as a needle, from apatient is essential to ensure patient safety.

Accordingly, efforts have been directed at designing apparatuses,devices, systems and methods for detecting changes in access conditions,such as in response to needle dislodgment, wherein detection issensitive, specific and immediate in response to such access changessuch that responsive measures can be suitably taken to minimize bloodloss from the patient due to same.

SUMMARY OF THE INVENTION

The present invention provides improved devices, apparatuses, systems,and methods for detecting dislodgment or disconnection of an accessdevice, such as dislodgment of a needle inserted in a patient duringdialysis therapy. The devices, apparatuses, systems, and methods of thepresent invention utilize an electrical circuit with a number ofelectrical contacts which are in fluid contact with the fluid circuitsuch that an electrical signal can be injected into at least a segmentincluding, for example, a loop defined along at least a portion of theconducting fluid circuit. In this regard, a direct-contact measurementcan be used to provide immediate detection of a change in an electricalvalue in response to a change in access conditions, such as a change inimpedance due to dislodgment of a needle or other access device from thepatient during medical therapy including, for example, dialysis therapyand medication delivery.

An advantage of the present invention is to provide an improved device,apparatus, system and/or method for detecting access disconnection.

A further advantage of the present invention is to provide an improveddevice, apparatus, system and/or method for detecting dislodgment of anaccess device from a patient during medical therapy including dialysistherapy.

Another advantage of the present invention is to provide an improveddevice, apparatus, method and/or system for detecting needle drop-outduring dialysis therapy.

Yet another advantage of the present invention is to provide asensitive, specific and responsive apparatus and/or device for detectingaccess disconnection during selfcare and home hemo treatments.

Moreover, an advantage of the present invention is to provide a viabledevice or apparatus for allowing a patient to self administer or othernon-medical personnel in a non-medical facility a dialysis therapy thatuses a portion of the patient's circulatory system.

Still further, an advantage of the present invention is to provide animproved apparatus for detecting access disconnection that uses a directconductivity measurement.

Yet still further, an advantage of the present invention is to providean access disconnection detection device, method and/or system thatemploys an electrical circuit in fluid and electrical contact with bloodflowing through a blood circuit allowing direct conductivitymeasurements to be made.

Furthermore, an advantage of the present invention is to provide animproved device, system and method for monitoring and/or controllingblood loss from a patient.

Another advantage of the present invention is an improved method fordialysis that employs an apparatus, device and/or system capable ofdetecting access disconnection, such as dislodgment of a needle insertedinto a patient through which blood flows during dialysis therapy andminimizing any resulting blood loss.

Yet another advantage of the present invention is an improved device forconnecting an electrical contact to a fluid circuit allowing fluid andelectrical communication between the electrical contact and fluidflowing through the fluid circuit.

Still another advantage of the present invention is an improvedapparatus, device, system and/or method for detecting accessdisconnection, such as needle drop-out during dialysis therapy, withenhanced sensitivity, accuracy and responsiveness.

Yet still another advantage of the present invention are improvedapparatuses, devices, systems and/or methods for the detection of fluidloss due to, for example, dislodgment of a single access device duringmedical therapies, for example, medication delivery and single needlehemo therapies.

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the following DetailedDescription of the Invention and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A illustrates a schematic view of an embodiment of the presentinvention showing two needles insertable within a patient through whichblood flows to and from an extracorporeal system.

FIG. 1B illustrates a schematic view of an embodiment of the presentinvention capable of detecting needle dislodgment during dialysistherapy.

FIG. 1C illustrates a perspective view of an embodiment of the presentinvention showing access disconnection detection capabilities duringmedical therapies administered via a single needle.

FIG. 2A illustrates an exploded view of an electrical contact couplingdevice in an embodiment of the present invention.

FIG. 2B illustrates a side sectional view of the coupling device of FIG.2A in an embodiment of the present invention.

FIG. 2C illustrates another embodiment of the coupling device of thepresent invention.

FIG. 2D illustrates another embodiment of the coupling device of thepresent invention showing a threaded engagement between the componentsof same.

FIG. 2E illustrates a sectional view of FIG. 2D.

FIG. 2F illustrates another embodiment of a coupling device of thepresent invention.

FIG. 3 schematically illustrates an embodiment of the present inventionrelating to processing of a measurable voltage signal to correct forchanges in baseline impedance during treatment.

FIG. 4A schematically illustrates a hemodialysis machine in anembodiment of the present invention.

FIG. 4B schematically illustrates a hemodialysis machine coupled to apatient's access via a tubing set in an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides medical devices, apparatuses, systems andmethods for detecting access disconnection. More specifically, thepresent invention provides medical devices, apparatuses, systems, andmethods that employ, in part, an electrical circuit with electricalcontacts in fluid contact and electrical communication with a fluidcircuit allowing a direct conductivity measurement to be used such thatdislodgment of a needle or other access device through which fluid flowsbetween a patient and the fluid circuit can be immediately detected. Inthis regard, fluid loss (i.e., blood loss) due to, for example,dislodgment of a needle from a patient undergoing medical treatment,such as dialysis therapy, medication delivery or the like, can becontrollably minimized.

It should be appreciated that the present invention is not limited tothe detection of needle dislodgment but can be utilized to detect thedislodgment or disconnection of any suitable access device. As usedherein, the term “access disconnection” or other like terms means anysuitable condition or event which can cause a loss or leak of anelectrically conductive fluid flowing along a fluid circuit connected tothe patient provided that a change in the electrical continuity betweenelectrical contacts coupled to the fluid circuit can be detected. Itshould be appreciated that a change in the electrical continuity asmeasured by an electrical value, such as impedance, may be detected evenin the absence of dislodgment of an access device from the patient. Theterm “access device” as used herein or other like terms means a suitabledevice that can be inserted within a patient such that fluid, includingblood, can pass to, through and/or from the patient via the accessdevice. The access device can include a variety of different andsuitable shapes, sizes and material make-up. Examples of an accessdevice includes needles, catheters, cannulas or the like. The accessdevice can be composed of any suitable material including, for example,stainless steel, plastic or like biocompatible materials.

Although in the embodiment set forth below the apparatus and/or deviceis designed for use in a dialysis therapy, such as hemodialysis,hemofiltration or hemodiafiltration, it should be noted that the presentinvention can be used in a number of different medical therapies thatemploy a variety of different and suitable fluid systems, such asextracorporeal blood systems. For example, the invention of the presentapplication can be used during intravenous infusion that can employ theuse of a single needle insertable within the patient for delivering amedical solution or drug, blood, blood products, processed blood or thelike between the patient and the fluid system. In addition, the presentinvention can be used in plasma exchange therapies, where a membrane isused to separate whole blood into plasma and cellular components.

With respect to dialysis therapy, the present invention can be used in avariety of different therapies to treat kidney failure. Dialysis therapyas the term or like terms are used throughout the text is meant toinclude and encompass any and all forms of therapies that utilize thepatient's blood to remove waste, toxins and excess water from thepatient. Such therapies include both intermittent, includinghemodialysis, hemofiltration and hemodiafiltration, and continuoustherapies used for continuous renal replacement therapy (CRRT). Thesecontinuous therapies include slow continuous ultrafiltration (SCUF),continuous veno venous hemofiltration (CVVH), continuous veno venoushemodialysis (CVVHD), and continuous veno venous hemodiafiltration(CVVHDF). Dialysis therapy can also include peritoneal dialysis, such acontinuous ambulatory peritoneal dialysis, automated peritoneal dialysisand continuous flow peritoneal dialysis. Further, although the presentinvention, in an embodiment, can be utilized in methods providing adialysis therapy for patients having chronic kidney failure or disease,it should be appreciated that the present invention can be used foracute dialysis needs, for example, in an emergency room setting. Lastly,as one of skill in the art appreciates, the intermittent forms oftherapy (i.e., hemofiltration, hemodialysis and hemodiafiltration) maybe used in the in center, self/limited care as well as the homesettings.

In an embodiment, the present invention includes an electrical circuitwith a number of electrical contacts, preferably a pair of electricalcontacts, in fluid contact and electrical communication with the fluidcircuit. The electrical contacts can include any suitable device throughwhich electrical connection can be made with the fluid circuit therebydefining a conductive pathway or conductor loop therein. Changes in anelectrical value or any suitable parameter associated with the conductorloop can then be monitored in response to changes in access conditionsas described below. In an embodiment, the electrical contact includes anelectrode which can be coupled to the fluid circuit such that anelectrical connection can be made in fluid contact with fluid flowingthrough the fluid circuit as discussed below.

For example, a constant current or other suitable electrical signal canbe injected into the fluid circuit via an electrode pair in contact withfluid flowing between the electrodes thereby defining a loop along atleast a portion of the fluid circuit. A change in an electrical value,preferably impedance, can then be measured in response to accessdisconnection. This can provide a direct conductivity measurementcapable of detecting a change in impedance or other suitable electricalparameter of the fluid, such as an electrically conductive fluidincluding blood, medical solutions or the like, as it flows between apatient and a fluid system (i.e., an extracorporeal blood system) via aneedle, needles or other access device(s) inserted within the patient.

In this regard, the present invention can effectively detect dislodgmentof a needle (e.g., a venous needle and an arterial needle) or otheraccess device through which blood or other suitable fluid can flow, forexample, to, through and from the patient, such as a blood circuit usedduring dialysis therapy. The detection capability of the presentinvention is believed to be immediate based on the measurable change in,for example, impedance of the electrically conductive fluid or fluidsdue to fluid loss resulting from disconnection of the access device fromthe patient.

The immediate detection capabilities of the present invention areimportant, particularly as applied to dialysis therapy where asignificant amount of blood loss can occur within a relatively shortperiod of time if delays in detection and responsive actions to stop theblood loss occur. Under typical dialysis conditions, if 20 seconds ormore time elapses before blood loss due to dislodgment is detected andstopped, over 100 milliliters of blood can be lost based on typicalblood flow rates of 400 milliliters/minute.

Applicants have discovered that the present invention can detect accessdisconnection, particularly in response to venous needle dislodgmentduring dialysis therapy, with a high degree of sensitivity andspecificity in addition to its immediate detection capabilities. Thedirect-contact measurement of the present invention is capable ofdetecting a change of an electrical value, preferably impedance, due toneedle dislodgment or the like as the blood flows through the bloodcircuit during dialysis therapy. As used herein, the term “electricalvalue” or other like terms means any suitable electrical parametertypically associated with electrical circuitry including, for example,impedance, resistance, voltage, current, rates of change thereof andcombinations thereof. The detection of a change in impedance or the likeis an indication that the needle has become dislodged or other likecondition has occurred. It is noted that the detection capabilities ofthe present invention can also effectively detect blood loss duringmedical therapy even if the needle or needles have not become dislodgedor at least not entirely dislodged. In this regard, the presentinvention can be effectively utilized to controllably minimize bloodloss from the patient based on the ability of the present invention toimmediately measure a change in impedance or the like due to blood losswith a high degree of sensitivity and specificity.

The devices and apparatuses of the present invention can include avariety of different components and configurations depending on theapplied medical therapy such that fluid loss, particularly blood lossdue to needle dislodgment or the like, can be effectively monitored.

Multiple Access Disconnection

Referring now to FIG. 1A, an embodiment of the apparatus 10 of thepresent invention includes a pair of electrical contacts 12 in fluidcontact with a blood tubing set 14 of a blood circuit 16. The bloodcircuit 16 connects a patient 18 to an extracorporeal blood system 20 asapplied to, for example, dialysis therapy including hemodialysis,hemofiltration, hemodiafiltration, continuous renal replacement or thelike or plasma therapies. The pair of electrical contacts 12 includes afirst electrical contact 22 and a second electrical contact 24 which areattached to a respective first tube member 26 and second tube member 28of the blood circuit 16. The first tube member 26 is connected to avenous needle or other suitable access device inserted into a vascularaccess region (not shown) of the patient. The second tube member 28 isconnected to an arterial needle or the like also inserted into avascular access region (not shown) of the patient. During dialysistherapy, for example, blood flows from the patient 18 through thearterial needle to the extracorporeal blood system 20 includes, forexample, a dialysis machine, via the second tube member 28 where theblood is treated and delivered to the patient 18 through the venousneedle via the first tube member 26.

As the blood flows through the blood circuit during dialysis therapy, aconstant electric current or the like generated by a controller 29 canbe injected or passed into the flowing blood via the electrical contactpair, preferably an electrode pair as described below. The electrodepair connected to the controller 29 or other suitable electronic devicecan then be used to measure a voltage change across an unknown fluid(e.g., blood) impedance or other like electrical value to detect achange in impedance or the like across the vascular access region. In anembodiment, one electrode can be used to inject the electrical signalinto the fluid circuit while the other electrode of the pair can be usedto sense a change in the electrical value and pass an electrical signalindicative of the same to the controller for processing and detectionpurposes. Upon dislodgment of at least one of the venous needle andarterial needle from the blood circuit or other suitable condition, animmediate and detectable increase in impedance or the like can bemeasured as compared to the impedance or other suitable parametermeasured under normal operating conditions.

It should be appreciated that the present invention as embodied in FIG.1A can be modified in a variety of suitable ways depending on themedical therapy as applied. For example, the venous and arterial needlescan be inserted into the vascular access of the patient on any suitablepart of the patient's body, such as the upper arm, lower arm, upperthigh area or the like during dialysis therapy. As previously discussed,the present invention can be applied to a variety of different medicaltherapies including intravenous infusions, plasma exchanges, medicationdelivery, drug delivery, blood delivery and dialysis therapies (i.e.,hemofiltration, hemodialysis, hemodiafiltration and continuous renalreplacement).

As illustrated in FIG. 1B, an embodiment of an apparatus 30 of thepresent invention is shown as applied during dialysis therapy. In anembodiment, the present invention includes a venous needle 32 andarterial needle 34 inserted within a patient access 36. The venousneedle 32 and arterial needle 34 are connected to the dialysis system 35via a number of tube members 38 that connect the various components ofthe dialysis system 35 including, for example, a venous drip chamber 40,a dialyzer 42, an arterial drip chamber 44 and a blood pump 46. Itshould be appreciated that one or more of the components of the dialysissystem can be provided within a dialysis machine coupled to the bloodcircuit. As shown in FIG. 1B, a first electrical contact coupling device48 and a second electrical contact coupling device 50 are positionedbetween the dialysis system 35 and the venous needle 32 and the arterialneedle 34. As used herein, the term “electrical contact couplingdevice,” “coupling device” or other like terms means any suitable devicethat can be used to connect an electrical contact to the fluid circuit.In an embodiment, the electrical contact coupling device can be used tocontact the electric contact to the fluid circuit allowing fluid contactand electrical connection with the fluid flowing through the fluidcircuit as described below.

In an embodiment, the electrical contact pair, preferably an electrodepair, are connected to a controller 52 or other suitable electronicdevice. The controller can be used to inject an electric signal via theelectrode pair and into the blood and/or other fluid as it flows throughthe blood circuit. This provides a conductor loop along which changes inelectrical parameters or values can be measured. The controller 52 whichis coupled to the electrode pair can also be used to measure thischange. It should be appreciated that the controller can include asingle electronic device or any suitable number of devices in electricalconnection with the electrical contacts to input an electrical signalinto the blood circuit thereby defining a conductor loop, to measure achange in an electrical parameter or value associated with the conductorloop and/or perform any other suitable tasks, such as processing thedetectable signal as discussed below.

Preferably, the electrical signal is generated from a constant currentthat is supplied to the electrodes until dislodgment occurs. The voltageacross an unknown impedance of the fluid (e.g., blood) circulatingthrough the blood circuit can then be measured (not shown) to detect achange in impedance due to changes in access conditions. However, itshould be appreciated that any suitable electrical parameter and changesthereof can be monitored to detect needle drop-out or the like aspreviously discussed.

As demonstrated below, the detection capabilities of the presentinvention are highly sensitive, specific and virtually immediate inresponse to access disconnection, such as needle dislodgment. Further,the electronic circuit of the present invention is relatively simple indesign such that preferably one electrode pair is necessary to conductdirect conductivity measurement. This can reduce costs and effort ascompared to known vascular access monitoring techniques that only employnon-invasive detection techniques, such as, capacitive couplers andinduction coils as previously discussed.

Applicants have discovered that the total impedance measured (“Z”) canbe modeled as two lumped impedances in parallel with one impedance(“Z_(D)”) being produced by the pump segment, the dialyzer, the dripchambers and/or other suitable components of the dialysis system and/orthe like. The other resistance impedance component (“Z_(P)”) is formedby the patient's vascular access and associated tubing which carriesblood to and from the vascular access and/or the like. In this regard,the total impedance measured can be characterized as a function of bothZ_(D) and Z_(P) as follows:

Z=(1/Z _(D)+1/Z _(P))⁻¹

Despite this parallel impedance, applicants have discovered that theelectrical contacts in connection with the controller can be used tomeasure a change in impedance along the conductor loop as blood flowsthrough the blood circuit in response to access disconnection, such asneedle dislodgment. If needle dislodgment occurs, the conductor loopalong at least a portion of the fluid circuit changes from a closedcircuit to an open circuit and thus Z=Z_(D) where Z_(P) approachesinfinity. In this regard, the direct conductive measurement capabilitiesof the present invention can be effectively used to detect accessdisconnection.

Applicants note that the Z_(D) component can produce a level ofelectrical interference associated with the time-varying high impedanceof the components of a medical system coupled to the fluid circuit, suchas a dialysis system and its components including, for example, a bloodpump, a drip chamber and/or the like. Applicants have discovered thatthe interference due to the Z_(D) component can be effectivelyeliminated, or at least reduced, if necessary. In an embodiment, thesignal associated with the detection of Z or the like can be furtherprocessed as discussed below. Alternatively, in an embodiment, theelectrical circuit of the present invention can be designed to block orbypass one or more components of the dialysis system from the conductorloop or pathway defined along the blood circuit as described below. Inthis regard, the accuracy, sensitivity and responsiveness with respectto the detection of access disconnection can be enhanced.

In an embodiment, a third electrical contact point 53 can be utilized tominimize or effectively eliminate the interferences with respect to thehigh impedance components coupled to the blood circuit, such as theblood pump and the like. The additional contact point can be made in anysuitable way. For example, the third contact point can be an electrodeor other suitable device through which electrical continuity can beestablished between it and one of the electrodes of the couplingdevices. In an embodiment, the third electrical contact can be attachedto a fluid circuit in fluid and electrical communication with fluidflowing through same.

The third contact point 53 can be positioned at any suitable positionalong the blood circuit. Preferably, the third contact point 53 ispositioned at any suitable location between the blood pump 46 and thecoupling device 50 as shown in FIG. 1B. An equalization potential canthen be applied between the third contact point 53 and the electrode ofthe coupling device 50. The potential is applied at a voltage that isequal to the potential applied between the electrodes of the firstcoupling device 48 and the second coupling device 50.

This effectively causes the electric current or the like, once injectedinto the blood circuit, to bypass one or more of the components of thedialysis system. In an embodiment, the third contact point 53 can bepositioned such that the electric current or the like would effectivelybypass all of the components of the dialysis system as shown in FIG. 1B.

Single Access Disconnection

The electrical contacts of the present invention can be positioned inany suitable location relative to the needle, needles or suitable accessdevice inserted within the patient. As illustrated in FIG. 1C, anembodiment of the present invention as applied with respect to thedetection of access detection, such as the dislodgment of a singleaccess device inserted within the patient is shown. This type ofapplication is applicable to a variety of different and suitable medicaltherapies administered via a single access device, such as a singleneedle, including intravenous infusion and dialysis therapy includinghemodialysis, hemofiltration, hemodiafiltration and continuous renalreplacement.

As applied, an electrically conductive fluid, such as blood, a bloodproduct, a medical fluid or the like flows between the patient and afluid system via a single access device. Dislodgment detection of asingle access device can include, for example, the detection of needledislodgment during the delivery of any suitable and electricallyconductive fluid or fluids including, for example, blood or medical drugor solution (i.e., a medication contained in an electrically conductivefluid, such as saline), processed blood, blood products, intravenoussolutions, the like or combinations thereof. The fluid delivery can bemade between an suitable container, such as blood bags or like fluiddelivery devices, and a patient. In this regard, immediate andresponsive detection of access disconnection via the present inventioncan be effectively utilized to monitor and control the transfer of bloodor a medical fluid, such as a medication or drug, during medical therapyadministered via a single needle.

As shown in FIG. 1C, an embodiment of the apparatus or device 54 of thepresent invention includes an access device 56; such as a needle,inserted into a blood vessel 58 within a needle insertion site 60 of thepatient 62. The needle 56 is connected to the fluid system 63, such as afluid infusion system, via a tube member 64. The infusion systemincludes, for example, an infusion pump 66 for transferring the blood orthe like from a container 68 (e.g., blood bag) to the patient. A firstelectrical contact 70 is spaced apart from the needle 56 along the tubemember 64 and a second electrical contact 72 is attached to the patientnear the insertion site 60. The first electrical contact 70 is in fluidcontact with the fluid as it flows from the delivery container 68 to thepatient.

In this configuration, the first and second electrical contacts,preferably electrodes, can be used to monitor changes in an electricalvalue, preferably impedance, within a loop formed by at least a portionof the fluid circuit as an electric signal passes therein. Theelectrical contact points can be coupled to an electronic device 74which is capable of processing a detectable signal transmitted throughthe electrodes in response to a change in impedance or the like due todislodgment of the single access device as described in detail below.Preferably, the electrical signal is generated by a constant currentsupplied to the electrodes such that a direct conductivity measurementcan be conducted to detect a change in impedance or the like in responseto changes in vascular access conditions, such as dislodgment of theaccess needle.

It is believed that the measured impedance, in the single needleapplication, is a function of both the impedance of the fluid (i.e.,blood) and the impedance as measured across the insertion site. In thisregard, the electronic device 74 can be adjusted to detect the impedanceat the level equivalent to the combined impedance of all items of theelectrical path (i.e., the conductive fluid in the tube, needle, bloodstream of venous vessel, body tissue, impedance across the skin withrespect to the sensing electrode 72 and the like).

Electrical Contacts

As previously discussed, the electrical contacts of the presentinvention are in fluid contact with the fluid as it flows through thefluid circuit. In this regard, the electrical contacts allow for adirect conductivity measurement which is capable of immediatelydetecting, with high sensitivity and specificity, a change (e.g., anincrease) in impedance or the like due to access disconnection, such asdislodgment of a venous needle (arterial needle or both) from the bloodcircuit during dialysis therapy.

The electrical contacts can be composed of any suitable conductive andbiocompatible material, such as, any suitable electrode materialincluding stainless steel, other suitable conductive materials orcombinations thereof. It is essential that the electrode material isbiocompatible.

It should be appreciated that the electrical contacts can be constructedin a variety of different shapes and sizes, illustrative examples ofwhich are described below. For example, the electrical contacts can beconfigured or designed as a plaster electrode which includes an agentcapable of expanding when in contact with moisture. The agent caninclude a variety of suitable materials including gels that are known toexpand more than ten times in volume upon contact with moisture.

In an embodiment, the plaster electrode can be utilized to detect fluid(i.e., blood leakage) at an insertion site of an access deviceinsertable within a patient during the administration of medical therapyvia a single access device as previously discussed. Upon contact withthe fluid, the plaster electrode would necessarily expand to such anextent that the electrode contact is broken, thus causing a detectableincrease in impedance of the fluid as it flows from the fluid system tothe patient via the needle.

In an embodiment, one or more electrodes (not shown), such as one ormore plaster electrodes as previously discussed, can be used incombination with the electrical contact pair as shown, for example, inFIGS. 1A and 1B. For example, a plaster electrode can be attached to thepatient near the insertion site of either or both of the arterial andvenous needles. In this regard, the plaster electrode(s) can be utilizedto detect leakage of fluid, such as blood, from the insertion site ofthe access device(s).

In an embodiment, an electrode pair is coupled to the blood circuit inan invasive manner (illustrated in FIGS. 2A-2C as discussed below) suchthat the electrodes contact the blood as previously discussed. Anexcitation source that includes a constant current source or the likecan be applied to the electrodes to inject an electric signal into theblood circuit thereby defining a conductor loop along which directconductivity measurements can be performed.

To ensure patient safety, the excitation source is typically isolatedfrom the instrument power. Preferably, the excitation source produces aconstant electrical current that passes through the blood via theelectrodes. Any suitable amount of current can be generated fordetection purposes. In an embodiment, the electrical current as itpasses through the blood is maintained at a level of about 10microamperes or less, preferably about 5 microamperes or less. It shouldbe appreciated that the present invention can be operated at low levelsof current (e.g., 10 microamperes or less) such that the level ofcurrent has negligible, if any, effect on the health and safety of thepatient.

It should be appreciated that the impedance or other suitable parametercan be measured and calculated in a variety of different and suitableways. For example, the amplitude, phase and/or frequency of the constantcurrent excitation source can be measured and varied during thedetection of a change in impedance. Impedance levels can then bedetected by measuring the voltage across the electrodes In this regard,the amplitude, frequency and/or phase of the voltage can then bemeasured and utilized in combination with the measured amplitude,frequency and/or phase of the excitation source to calculate bloodimpedance levels based on derivations or equations which are typicallyused to calculate impedance.

The electrical contacts can be connected to the blood circuit in avariety of different and suitable ways. For example, the electricalcontacts can be an integral component of the extracorporeal system, adisposable component that can be connected and released from the tubingmembers of the blood circuit, a reusable component that can beautoclaved between uses, or the like.

Electrical Contact Coupling Device

In an embodiment, the apparatus of the present invention includes anelectrical contact coupling device that can be utilized to secure theelectrical contacts, preferably electrodes, to the blood circuit suchthat the electrodes effectively contact the blood and, thus, can be usedto effectively monitor changes in access conditions as previouslydiscussed. The coupling device of the present invention can also bedesigned to facilitate the protection of the user against contact withpotential electrical sources. In an embodiment, the device can include aconductive element connected to the tube through which a medical fluid,such as blood, can flow wherein the conductive element has a firstportion exposed to the medical fluid and a second portion external tothe tube.

The coupling device of the present invention can include a variety ofdifferent and suitable configurations, components, material make-up orthe like. In an embodiment, the present invention can include a devicefor connecting an electrical contact to a fluid conduit providing fluidand electrical communication between the electrical contact and fluidflowing through the fluid conduit. The device can include a first memberincluding an annular portion capable of accommodating the electricalcontact and a first stem portion connected to the annular member whereinthe stem portion has an opening extending therethrough to the annularportion; a second member including a base portion with a groove regionand a second stem portion with an opening extending therethrough to thegroove region allowing the first member to be inserted and secured tothe second member; and a contact member adapted to fit the first andsecond stem portions allowing the contact member to abut against atleast a portion of the electrical contact member allowing an electricalconnection to be made between the electrical contact and the contactmember. Illustrative examples of the electrical contact coupling deviceof the present invention are described below.

As illustrated in FIGS. 2A and 2B, the electrical contact couplingdevice 80 includes a probe member 82 that has a cylindrical shape withan opening 84 extending therethrough. In this regard, an electricalcontact, preferably an electrode 86 having a cylindrical shape can beinserted into the opening 84 such that the electrode 86 is secure withinthe probe member 82. In an embodiment, the probe member 82 has a channel85 extending along at least a portion of the opening 84 within which theelectrode 86 can be inserted into the probe member 82. A tube member,for example, from a blood tubing set, connector tube member of adialysis machine or the like, can be inserted into both ends of theopening 84 of the probe member 82 in contact with an outer portion ofthe channel 85 allowing blood or other suitable fluid to make fluidcontact with the electrode 86 in any suitable manner. The electrode 86has an opening 88 that extends therethrough within which blood (notshown) or other suitable fluid from the fluid circuit can flow. In anembodiment, the diameter of the opening 88 of the electrode 86 is sizedto allow blood flow through the electrode 86 such that blood flow levelsunder typical operating conditions, such as during dialysis therapy, canbe suitably maintained. In this regard, the coupling device of thepresent invention can be readily and effectively attached to a fluidcircuit, including a blood circuit or the like, for use during medicaltherapy including, for example, dialysis therapy. It should beappreciated that the coupling device 80 of the present invention can beattached to the fluid circuit in any suitable way such that electricaland fluid connection can be made with the fluid flowing through thefluid circuit.

The probe member 82 also includes a stem portion 90 that extends from asurface 92 of its cylindrical-shaped body. The stem portion 90 has anopening 93 that extends therethrough. In an embodiment, the stem portion90 is positioned such that at least a portion of the electrode 86 is incontact with the opening 93 of the stem portion 90.

In order to secure the electrode 86 to the blood circuit, the couplingdevice 80 includes a socket member 94 that includes a body portion 96with an opening 98 for accepting the probe member 82 and for accepting ablood tube member (not shown) of the blood circuit such that blooddirectly contacts the electrode as it circulates through the bloodcircuit during dialysis therapy. In an embodiment, the socket member 94includes a stem portion 100 extending from the body member 96 whereinthe stem portion 100 includes an opening 102 extending therethrough. Asthe probe member 82 is inserted through the opening 98 of the bodymember 96, the stem portion 90 of the probe member 82 can be insertedinto the opening 102 of the stem portion 100 of the body 96 of thesocket member 94.

In an embodiment, the socket member 94 includes a groove region 104extending along at least a portion of the body 96 of the socket member94. In this regard, the probe member 82 can be inserted through theopening 98 and then moved or positioned into the groove region 104 tosecure the probe member 82 within the body 96 of the socket member 94.

In an embodiment, the coupling device 80 includes an electrical contactmember 106 that is inserted within the opening 102 of the stem portion100 of the body 96 of the socket member 94 such that the electricalcontact member 106 extends through the opening 93 of the stem portion 90of the probe member 82 to contact at least a portion of a surface 108 ofthe electrode 86.

The electrical contact member 106 is utilized to connect the electronics(not shown) of, for example, the excitation source, a signal processingdevice, other like electronic devices suitable for use in monitoringand/or controlling changes in access conditions, such as needledislodgment. The electrical contact member 106 can be made of anysuitable material, such as any suitable conductive material including,stainless steel, other like conductive materials or combinationsthereof. In order to secure the electrical contact member 106 in place,a contact retainer member 110 is inserted within the opening 102 of thestem portion 100 at an end region 112 thereof.

In an embodiment, the coupling device is mounted to a dialysis machine,device or system in any suitable manner. For example, the couplingdevice can be mounted as an integral component of the dialysis machine.As well, the coupling device can be mounted as a separate and/or standalone component which can interface with any of the components of theapparatus and system of the present invention. In an embodiment, thecoupling device 80 can be insertably mounted via the stem portion 100 ofthe socket member 94 to a dialysis machine or other suitable components.

It should be appreciated that the electrical contact coupling device caninclude a variety of different and suitable shapes, sizes and materialcomponents. For example, another embodiment of the coupling device isillustrated in FIG. 2C. The coupling device 114 in FIG. 2C is similar inconstruction to the coupling device as shown in FIGS. 2A and 2B. In thisregard, the coupling device 114 of FIG. 2C can include, for example, acylindrical-shaped electrode or other suitable electrical contact, aprobe member for accepting the electrode and securing it in place withina socket member of the sensing device. The probe member includes a stemportion that is insertable within a stem portion of the socket member.An electrical contact member is insertable within the stem portion suchthat it can contact the electrode. The coupling device of FIG. 2C canalso include a contact retainer member to hold the electrical contactmember in place similar to the coupling device as shown in FIGS. 2A and2B.

As shown in FIG. 2C, the probe member 116 of the electrical contactcoupling device 114 includes a handle 118 which can facilitate securingthe probe member 116 within the socket member 120. The handle 118, asshown, has a solid shape which can facilitate the use and manufacture ofthe coupling device 114. In addition, the stem portion (not shown) ofthe probe member 116 is larger in diameter than the stem portion of theprobe member as illustrated in FIG. 2A. By increasing the stem size, theprobe member can be more easily and readily inserted within the socketmember. Further, the probe member is greater in length as compared tothe probe member as shown in FIGS. 2A and 2B such that the end regions122 of the probe member 116 extend beyond a groove region 124 of thesocket member 120. This can facilitate securing the probe member withinthe groove region 124 of the socket member 120.

In an embodiment, an opening 126 of the socket member 120 can include anadditional opening portion 128 to accommodate the insertion of the stemportion of the probe member 116, having an increased size, therethrough.This can ensure proper alignment of the probe member with respect to thesocket member before insertion of the probe member into the socketmember thus facilitating the insertion process.

It should be appreciated that the probe member, socket member andcontact retainer member can be composed of a variety of different andsuitable materials including, for example, plastics, molded plastics,like materials or combinations thereof. The various components of thecoupling device, such as the probe member, socket member and contactretainer member, can be fitted in any suitable way. For example, thecomponents can be fitted in smooth engagement (as shown in FIGS. 2A and2B), in threaded engagement (as shown in FIGS. 2D and 2E) and/or anysuitable fitting engagement or arrangement to one another.

As shown in FIGS. 2D and 2E, the coupling device 130 of the presentinvention can be made of threaded parts which are removably connected toone another to form the coupling device. The threaded parts canfacilitate securing the electrode to the blood circuit as well asgeneral use of same as described below.

In an embodiment, the stem portion 132 of the body 134 of the couplingdevice 130 has a threaded region 136 which can be insertably attached toa dialysis machine or other suitable mounting device in threadedengagement. This can facilitate the ease in which the coupling device isattached and detached from the mounting device.

As shown in FIG. 2E, the stem portion 132 is threaded on both sidesallowing it to be in threaded engagement with an annular member 138. Theannular member 138 provides direction and support allowing theelectrical contact member 140 to abut against the electrode 142 housedin the probe member 144 as previously discussed.

In an embodiment, a plate member 146 made of any suitable conductivematerial can be depressed against a spring 148 as the probe member 144is secured to the body 134. At the same time, another spring 150 can bedisplaced against the electrical contact member 140 in contact with theretainer 152 which is inserted within an annular region of the annularmember 138 to secure the electrical contact member 140 to the body 134.

The spring mechanism in an embodiment of the present invention allowsthe parts of the coupling device 130 to remain in secure engagementduring use. It can also facilitate use during detachment of the partsfor cleaning, maintenance or other suitable purpose.

In an embodiment, the coupling device can include a device with anelectrical contact attached allowing the electrical contact to pierce orpuncture the a fluid conduit when the device is movably attached to thefluid conduit. In this regard, the device can act through a clampingmechanism to allow electrical and fluid communication between theelectrical contact and fluid flowing through the fluid conduit. Thedevice can be coupled to a controller or the like allowing detection ofaccess disconnection using direct conductive measurement during medicaltherapy, such as dialysis therapy, as previously discussed. The devicecan be made in a variety of suitable ways.

In an embodiment, the device 153 includes a first member 154 and asecond member 155 movably attached to the first member 154 at an end 156as shown in FIG. 2F. The first and second members can be attached in anysuitable way, such as by a hinge 157 or other suitable mechanism thatcan allow movement of the first and second members such that the device153 can be attached to a fluid conduit. The movable members of thedevice 153 can be composed of any suitable material, preferably aconductive material, such as stainless steel, that is compatible withthe electrical contact such that an effective electrical connection canbe made.

The electrical contact 158 can be composed of any suitable material,such as stainless steel, as previously discussed. The electrical contactmaterial defines a shape and is attached to a portion of the first orsecond members in any suitable way. This allows the electrical contact158 to puncture or pierce a fluid conduit when the device 158 isattached thereto such that the electrical contact 158 can makeelectrical and fluid contact with fluid flowing through the conduit.

In an embodiment, the device 158 is self-sealing upon attachment to thefluid conduit. This can be done in any suitable way, such as by applyingany suitable adhesive, gel or other sealing material to the device 158,if necessary, prior to attachment to the fluid conduit. In this regard,the device 153 provides a simple design that can be effectively andreadily used to provide both fluid and electrical contact between anelectrical contact and fluid flowing through a fluid conduit, such as ablood circuit.

As previously discussed, the present invention can be effectivelyutilized to detect dislodgment of an access device, such as a needle,inserted within a patient through which fluid can pass between thepatient and a fluid delivery and/or treatment system. The presentinvention can be applied in a number of different applications, such asmedical therapies or treatments, particularly dialysis therapies. Indialysis therapies, access devices, such as needles, are inserted into apatient's arteries and veins to connect blood flow to and from thedialysis machine.

Under these circumstances, if the needle becomes dislodged or separatedfrom the blood circuit, particularly the venous needle, the amount ofblood loss from the patient can be significant and immediate. In thisregard, the present invention can be utilized to controllably andeffectively minimize blood loss from a patient due to dislodgment of theaccess device, such as during dialysis therapy including hemodialysis,hemofiltration, hemodiafiltration and continuous renal replacement.

Signal Detection and Processing

As previously discussed, the electrical contacts in connection with thecontroller can be used to detect a change in impedance or the like inresponse to needle drop-out or other like changes in access conditions.In an embodiment, the present invention can be adapted to correct forany variations in the baseline impedance over time. This can increasethe level of sensitivity with respect to the detection capabilities ofthe present invention. In this regard, if changes in the baselineimpedance are too great and not adequately corrected for, changes inimpedance due to needle dislodgment may not be as readily, if at all,detectable above baseline values.

From a practical standpoint, there are a number of different processconditions that may influence a change in the baseline impedance overtime. For example, a gradual drift or change in the baseline can occurdue to a change in the characteristics, such as the hematocrit, plasmaprotein, blood/water conductivity and/or the like, of the blood or othersuitable fluid during treatment. This can arise due to changes in thelevel of electrolytes or other components during dialysis therapy.

As illustrated in FIG. 3, the present invention can process a measurablevoltage signal to correct for changes in baseline impedance over time.This can enhance the detection capabilities of the present invention aspreviously discussed. In an embodiment, a current source 160 or the likegenerates an electric current to pass through the blood as it circulatesinto, through and out of the patient along the extracorporeal bloodcircuit 162 which connects the patient via venous and arterial needlesto the dialysis system including a variety of process components. Theelectric current is injected into the blood circuit via a firstelectrical contact 163 a thereby defining a conductor loop or pathwayalong the blood circuits. Preferably, the current is maintained at aconstant level until dislodgment occurs. The second electrode 163 b isused to sense voltage or the like along the conductor loop and then passa signal indicative of same and/or changes thereof to an electronicdevice for detection and processing as previously discussed. The voltagesignal can be measured and processed in any suitable manner.

In an embodiment, the signal is passed through a series of componentsincluding a filter or filters 164 which can act to filter noise from thesignal, particularly noise derived from the rotation from the pump inorder to minimize a false negative and/or positive detection of needledislodgment, a rectifier 166, a peak detector 168 and an analog todigital converter (“ADC”) 170 to digitize the signal. In this regard,the digital signal can then be stored in a computer device (not shown)for further processing. The voltage signal is continually measured andprocessed over time. With each measurement, the digitized signals arecompared to evaluate changes due to baseline changes associated withvariations in process conditions over time, such as a change in thecharacteristics of blood as previously discussed. If a baseline changeis determined, the digitized signal can be further processed to correctfor the change in baseline.

The voltage data is continually sent to a control unit 172 coupled tothe ADC. The control unit continually performs a calculation todetermine whether a change in impedance or the like in response toneedle dislodgment has occurred. In an embodiment, dislodgment of anaccess device is detected when [V(t)−V(t−T)]>C1, where t is time, whereT is the period of blood pump revolution, where C1 is a constant andwhere V(t)=I_(o)*Z, where I_(o) is current and where Z is the impedanceof the bloodline which is a function of the impedance associated withpatient's vascular access and the impedance associated with variouscomponents of the dialysis system, such as the dialyzer, as previouslydiscussed.

If disconnection of the patient from the blood circuit is detected, thecontrol unit 172 can be utilized to process the signal in order tominimize blood loss from the patient. In an embodiment, the controlleris in communication with a dialysis system as applied to administerdialysis therapy including, for example, hemodialysis, hemofiltration,hemodiafiltration and continuous renal replacement. This communicationcan be either hard-wired (i.e., electrical communication cable), awireless communication (i.e., wireless RF interface), a pneumaticinterface or the like. In this regard, the controller can process thesignal to communicate with the dialysis system or device to shut off orstop the blood pump 174 associated with the hemodialysis machine andthus effectively minimize the amount of blood loss from the patient dueto needle dislodgment during hemodialysis.

The controller can communicate with the dialysis system in a variety ofother ways. For example, the controller and hemodialysis machine cancommunicate to activate a venous line clamp 176 for preventing furtherblood flow via the venous needle thus minimizing blood loss to thepatient. In an embodiment, the venous line clamp is activated by thecontroller and attached to or positioned relative to the venous needlesuch that it can clamp off the venous line in close proximity to theneedle. Once clamped, the dialysis system is capable of sensing anincrease in pressure and can be programmed to shut-off the blood pumpupon sensing pressure within the blood flow line which is above apredetermined level. Alternatively, the venous line clamp can becontrollably attached to the dialysis system.

In an embodiment, an alarm can be activated upon detection of blood lossdue to, for example, needle dislodgment during dialysis therapy. Onceactivated, the alarm (i.e., audio and/or visual or the like) is capableof alerting the patient, a medical care provider (i.e., doctor,registered nurse or the like) and/or a non-medical care provider (i.e.,family member, friend or the like) of the blood loss due to, forexample, needle dislodgment. The alarm function is particularlydesirable during dialysis therapy in a non-medical facility, such as ina home setting or self care setting where dialysis therapy is typicallyadministered by the patient and/or a non-medical care provider in anon-medical setting or environment excluding a hospital or other likemedical facility.

In this regard, the alarm activation allows, for example, the patient toresponsively act to ensure that the dialysis therapy is terminated by,for example, to check that the blood pump has been automatically shutoff to minimize blood loss to the patient. Thus, the patient has theability to act without the assistance of a third party (i.e., to act onhis or her own) to ensure that responsive measures are taken to minimizeblood loss. The alarm can thus function to ensure the patient's safetyduring the administration of dialysis therapy, particularly as appliedto home hemo treatments where at least a portion of the dialysis therapycan be administered while the patient is sleeping.

Dialysis Machine

As previously discussed, the present invention can be adapted for usewith any suitable fluid delivery system, treatment system or the like.In an embodiment, the present invention is adapted for use with adialysis machine to detect access disconnection as blood flows betweenthe patient and the dialysis machine along a blood circuit duringtreatment, including, for example hemodialysis, hemofiltration andhemodiafiltration.

The present invention can include any suitable dialysis machine for suchpurposes. An example, of a hemodialysis machine of the present inventionis disclosed in U.S. Pat. No. 6,143,181 herein incorporated byreference. In an embodiment, the dialysis machine 190 comprises a mobilechassis 192 and it has at the front side 194 thereof with a commonmechanism 196 for connecting tubing or the like by which a patient canbe connected to the dialysis machine as shown in FIG. 4A. A flat touchscreen 197 which can show several operational parameters and is providedwith symbols and fields for adjustment of the dialysis machine byrelevant symbols and fields, respectively, on the screen being touchedcan be adjusted vertically and can be universally pivoted on thedialysis machine and can be fixed in the desired adjusted position.

In an embodiment, the dialysis machine includes a chassis having one ormore connectors for connecting a patient to the dialysis machine via ablood circuit allowing blood to flow between the patient and thedialysis machine during dialysis therapy wherein one or more electricalcontacts are connected to the blood circuit in fluid communication withthe blood allowing detection of a change in an electrical value inresponse to access disconnection as the blood flows through the bloodcircuit having an electrical signal passing therein.

In an embodiment, the dialysis machine of the present invention can bedesigned to accommodate one or more of the electrical contact couplingdevices, such as a pair of coupling device, used to detect accessdisconnection as shown in FIG. 4B. For example, one or more couplingdevices 198 can be attached to the front panel 194 of the dialysismachine 190. This can be done in any suitable way. In an embodiment, thea stem portion of the coupling device is insertably mounted via athreaded fit, frictional fit or the like, as previously discussed. Thisconnects the patient to the dialysis machine 190 via a blood tubing set202. The blood tubing set includes a first blood line 204 and a secondblood line 206. In an embodiment, the first blood line 204 is connectedto the patient via an arterial needle 208 or the like through whichblood can flow from the patient 200 to the dialysis machine 190. Thesecond blood line 206 is then connected to the patient 200 via a venousneedle 210 or the like through which fluid flows from the dialysismachine to the patient thereby defining a blood circuit. Alternatively,the first blood line and the second blood line can be coupled to thevenous needle and the arterial needle, respectively. The blood lines aremade from any suitable medical grade material. In this regard, accessdisconnection, such as dislodgment of an arterial needle and/or a venousneedle can be detected as previously discussed. Alternatively, thecoupling device can be attached to the blood tubing set which is thenattached to the dialysis machine in any suitable way.

Dialysis Treatment Centers

As previously discussed, the present invention can be used duringdialysis therapy conducted at home and in dialysis treatment centers.The dialysis treatment centers can provide dialysis therapy to a numberof patients. In this regard, the treatment centers include a number ofdialysis machines to accommodate patient demands. The therapy sessionsat dialysis treatment centers can be performed 24 hours a day, sevendays a week depending on the locale and the patient demand for use.

In an embodiment, the dialysis treatment centers are provided with thecapability to detect access disconnection during dialysis therapypursuant to an embodiment of the present invention. For example, one ormore of the dialysis machines can be adapted for use with an electricalcontact coupling device along with the necessary other components todetect access disconnection as previously discussed.

In an embodiment, the electrical contact coupling device can be directlyattached to one or more of the dialysis machines of the dialysistreatment center. It should be appreciated that the apparatuses,devices, methods and/or systems pursuant to an embodiment of the presentinvention can be applied for use during dialysis therapy administered toone or more patients in the dialysis treatment center in any suitableway. In an embodiment, the treatment center can have one or more patientstations at which dialysis therapy can be performed on one or morepatients each coupled to a respective dialysis machine. Any suitablein-center therapy can be performed including, for example, hemodialysis,hemofiltration and hemodiafiltration and combinations thereof. As usedherein, the term “patient station” or other like terms mean any suitablydefined area of the dialysis treatment center dedicated for use duringdialysis therapy. The patient station can include any number and type ofsuitable equipment necessary to administer dialysis therapy.

In an embodiment, the dialysis treatment center includes a number ofpatient stations each at which dialysis therapy can be administered toone or more patients; and one or more dialysis machines located at arespective patient station. One or more of the dialysis machines caninclude a chassis having one or more connectors for connecting a patientto the dialysis machine via a blood circuit allowing blood to flowbetween the patient and the dialysis machine during dialysis therapywherein a pair of electrical contacts are connected to the blood circuitin fluid communication with the blood allowing detection of a change inan electrical value in response to access disconnection as the bloodflows through the blood circuit having an electrical signal passingtherein.

As previously discussed, the access disconnection detection capabilitiesof the present invention can be utilized to monitor and control a safeand effective dialysis therapy. Upon dislodgment of an access device,such as a needle, from the patient, the direct conductive measurementcapabilities of the present invention can be used to provide a signalindicative of dislodgment that can be further processed for controland/or monitoring purposes. In an embodiment, the signal can be furtherprocessed to automatically terminate dialysis therapy to minimize bloodloss due to dislodgment as previously discussed. Further, the signal canbe processed to activate an alarm which can alert the patient and/ormedical personnel to the dislodgment condition to ensure that responsivemeasures are taken. It should be appreciated that the present inventioncan be modified in a variety of suitable ways to facilitate the safe andeffective administration of medical therapy, including dialysis therapy.

Applicants have found that the direct conductive measurementcapabilities of the apparatus of the present invention can immediatelydetect blood loss or the like due to access disconnection, such asneedle dislodgment, with high sensitivity and selectivity such thatresponsive measures can be taken to minimize blood loss due to same. Theability to act responsively and quickly to minimize blood loss upondetection thereof is particularly important with respect to needledislodgment during hemodialysis. If not detected and responded toimmediately, the amount of blood loss can be significant. In anembodiment, the present invention is capable of taking active orresponsive measures, to minimize blood loss (i.e., shut-off blood pump,activate venous line clamp or the like) within about three seconds orless, preferably within about two to about three second upon immediatedetection of needle dislodgment.

In addition, the controller can be utilized to monitor and/or controlone or more treatment parameters during hemodialysis. These parameterscan include, for example, the detection of blood due to blood loss uponneedle dislodgment, the change in blood flow, the detection of airbubbles in the arterial line, detection of movement of the sensor duringtreatment, detection and/or monitoring of electrical continuity of thesensor or other like treatment parameters. In an embodiment, thecontroller includes a display (not shown) for monitoring one or more ofthe parameters.

As used herein “medical care provider” or other like terms including,for example, “medical care personnel”, means an individual orindividuals who are medically licensed, trained, experienced and/orotherwise qualified to practice and/or administer medical proceduresincluding, for example, dialysis therapy, to a patient. Examples of amedical care provider include a doctor, a physician, a registered nurseor other like medical care personnel.

As used herein “non-medical care provider” or other like termsincluding, for example, “non-medical care personnel” means an individualor individuals who are not generally recognized as typical medical careproviders, such as doctors, physicians, registered nurses or the like.Examples of non-medical care providers include patients, family members,friends or other like individuals.

As used herein “medical facility” or other like terms including, forexample, “medical setting” means a facility or center where medicalprocedures or therapies, including dialysis therapies, are typicallyperformed under the care of medical care personnel. Examples of medicalfacilities include hospitals, medical treatment facilities, such asdialysis treatment facilities, dialysis treatment centers, hemodialysiscenters or the like.

As used herein “non-medical facility” or other like terms including, forexample, “non-medical setting” means a facility, center, setting and/orenvironment that is not recognized as a typical medical facility, suchas a hospital or the like. Examples of non-medical settings include ahome, a residence or the like.

It should be appreciated that the electrode output signal can becombined with other less sensitive blood loss detection methods, such asvenous pressure measurements, systemic blood pressure, the like orcombinations thereof, to improve specificity to needle dislodgment.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its intended advantages. It is therefore intendedthat such changes and modifications be covered by the appended claims.

The invention is claimed as follows:
 1. A dialysis system comprising: ablood circuit including a blood pump, a dialyzer, and an air removalapparatus; an arterial line of the blood circuit extending from theblood pump to an arterial access needle; a venous line of the bloodcircuit extending from the air removal apparatus to a venous accessneedle; arterial and venous conductive connections placed along thearterial and venous lines, respectively; a first electrical potentialsource configured to apply a first electrical potential between (i) thearterial and venous conductive connections and (ii) the arterial andvenous access needles; and a second electrical potential sourceconfigured to apply a second electrical potential between (a) thearterial and venous conductive connections and (b) one of the bloodpump, dialyzer or air removal device.
 2. The dialysis system of claim 1,wherein the second electrical potential is applied between the arterialconductive connection and the blood pump.
 3. The dialysis system ofclaim 1, wherein the second electrical potential is applied between thearterial conductive connection and a third conductive connection placedalong the blood circuit.
 4. The dialysis system of claim 3, wherein thethird conductive connection is located along the arterial line betweenthe arterial conductive connection and the blood pump.
 5. The dialysissystem of claim 1, wherein the second electrical potential is appliedbetween the venous conductive connection and the air removal apparatus.6. The dialysis system of claim 1, wherein the second electricalpotential is applied between the venous conductive connection and athird conductive connection placed along the blood circuit.
 7. Thedialysis system of claim 6, wherein the third conductive connection islocated along the venous line between the venous conductive connectionand the air removal apparatus.
 8. The dialysis system of claim 1, whichis configured such that the second electrical potential at leastsubstantially matches the first electrical potential.
 9. The dialysissystem of claim 1, which includes electronics configured to measure thefirst electrical potential and a controller programmed to at leastsubstantially match the second electrical potential to the measuredfirst electrical potential.
 10. The dialysis system of claim 1, whichincludes a controller configured to determine a needle disconnectionupon a threshold change in a signal produced by the first electricalpotential.
 11. The dialysis system of claim 1, wherein the secondelectrical potential causes a signal produced by the first electricalpotential to bypass at least one of the blood pump, dialyzer or airremoval apparatus.
 12. A dialysis system comprising: a blood circuitincluding a dialyzer, a blood pump, an arterial line and a venous line;arterial and venous conductive connections placed along the arterial andvenous lines between the dialyzer/blood pump and the distal ends of thearterial and venous lines, respectively; a first electrical potentialsource configured to apply a first electrical potential between (i) thearterial and venous conductive connections and (ii) the distal ends ofthe arterial and venous lines; and a second electrical potential sourceconfigured to apply a second electrical potential between (a) thedialyzer/blood pump and (b) the arterial and venous conductiveconnections.
 13. The dialysis system of claim 12, wherein the secondelectrical potential at least substantially matches the first electricalpotential, causing a signal produced by the first electrical potentialto bypass at least one of the dialyzer or the blood pump.
 14. Thedialysis system of claim 12, which includes a controller programmed todetermine a needle access disconnection upon a sufficient change in asensed signal produced by the first electrical potential.
 15. An accessdisconnection method for a machine employing a blood circuit, the bloodcircuit having a machine segment and a patient access segment, themethod comprising: injecting an electrical signal into the blood circuitbetween the machine segment and the patient access segment; attemptingto cause the electrical signal to flow through only the patient accesssegment and to bypass the machine segment; and measuring the signal inthe patient access segment and determining that an access disconnectionevent has occurred upon a threshold change in the measured signal. 16.The access disconnection method of claim 15, wherein attempting to causethe electrical signal to bypass the machine segment includes applying apotential to the blood circuit at a location between the signal in thepatient access segment and a machine operating component of the machinesegment of the blood circuit.
 17. The access disconnection method ofclaim 16, wherein applying the potential includes applying a potentialthat is at least substantially equal to a potential applied to cause thesignal.
 18. The access disconnection method of claim 15, the signalapplied via first and second conductive connections to the bloodcircuit, and wherein attempting to cause the electrical signal to bypassthe machine segment includes applying a potential to the blood circuitat a location between one of the first and second conductive connectionsand a machine operating component of the machine segment of the bloodcircuit.
 19. The access disconnection method of claim 18, which includesapplying the potential to one of the first and second conductiveconnections and a third conductive connection located between the one ofthe first and second connections and the machine operating component.20. The access disconnection method of claim 15, wherein attempting tocause the electrical signal to bypass the machine segment includes, inaddition to the signal, applying a potential to the blood circuitdownstream of the blood pump.
 21. The access disconnection method ofclaim 15, which includes taking into account an impedance associatedwith the vascular access in determining the threshold change in themeasured signal by which the access disconnection is determined.